1. Field of the Invention
The invention relates to a measuring instrument for determining the scattering and absorption coefficient of the atmosphere, having a light emitter on the emitter side, and on the receiver side having a light detector and an infrared sound receiver for emitter light attenuated in the atmosphere, and having instruments for measuring the intensity of the received, scattered light and the absorbed light. In this document, such a measuring instrument will also be called an extinction meter.
2. The Prior Art
An extinction coefficient is made up of the sum of a spectral scattering coefficient and an absorption coefficient; these coefficients are important basic variables of the atmosphere. Flight tests of these basic variables determined by means of an extinction meter, or in other words measurements of such variables made from aircraft, are of particular significance for assessing the anthropogenic and natural loading of the air for lidar measurements, for a radiation balance, for optical depth, icing, turbulence, visibility, slant range visibility, and so forth.
Conventional instruments function either as visual range or scattered light meters and typically include an integrating nephelometer. Transmissometers must measure through a distance that is adapted to the measured value. Scattered light meters, also known as integrating nephelometers, in which the scattering in the atmosphere is summed up over a wide range of angles, have been known for a long time. This kind of scattered light plotter is for instance described by G. H. Ruppersberg in an article entitled "Registrierung der Sichtweite mit dem Streulichtschreiber" [Recording of Visual Range with the Scattered Light Plotter], issued as a reprint from "Beitrage zur Physik der Atmosphare" [Atmospheric Physics Journal] 37, 3/4, 1964, pp. 252-263, published by the Akademische Verlagsgesellschaft Frankfurt am Main, 1964. An integrating nepheloemeter is discussed both by R. G. Beuttel and A. W. Brewer in "Instruments for the Measurement of the Visual Range" in the Journal of Scientific Instruments 26 (1949), pp. 357-359 and by R. J. Charlson, H. Horvath and R. S. Pueschel in "The Direct Measurement of Atmospheric Light Scattering Coefficient for Studies of Visibility and Pollution", Environment, Vol. 1, pp. 469-478.
With these instruments, however, only the scattering coefficient, but not the extinction coefficient, can be measured; the extinction coefficient must be measured exactly, for instance for a visibility determination by the Koschmieder theory, because the absorption cannot be determined with these instruments.
For specialized probes of the atmosphere, aircraft-worthy integrating nephelometers are needed (that is, integrating nephelometers that can be accommodated in or on aircraft) which vary the aerosol to be measured as little as possible. Such variations may for instance arise from heating and/or turbulence; moreover, a flow in curved channels can cause a false reading of the particle size distribution, as is the case with equipment on the market or modified research equipment.
Known aircraft-worthy integrating nephelometers also lack genuine calibration during the measurement. Although measurement takes place over a wide range of angles, it is not done below and above an angle of 9.degree. and 170.degree. respectively. The maximum for the integrant of the condition equation for the absolute scattering function with the aid of which the scattering coefficient can be ascertained occurs at approximately 10.degree. to 20.degree. for average scattering functions.